It is known that conductive materials are obtained by doping electron donating molecules or electron accepting molecules into conjugated polymers as organic conductive materials, including polyacetylene, polypyrrole, polyallylenevinylene, polythienylenevinylene, etc. It is also known that electron transfer complexes formed by the combination of electron donating molecules such as tetrathiafulvalene, bisethylenedithiotetrathiafulvalene, etc. and electron accepting molecules such as tetracyanoquinodimethane, tetracyanoethylene, etc. exhibit a conductive property. Some of these organic conductive materials show high conductivity but can form a thin film only with difficulty. Furthermore, these conductive materials involve a problem in terms of stability, since they are readily oxidized in the air.
Since condensed polycyclic aromatic compounds like polyacenes such as anthracene, naphthacene, pentacene, etc. are conjugated polymers, it is known that these compounds exhibit a conductive property by doping electron donating molecules or electron accepting molecules into these compounds. It has thus been expected to use these compounds as electronic industry materials. Also, as the number of condensed benzene rings in polyacenes increases, the band gap between HOMO and LUMO decreases theoretically so that it is expected to increase the conductive property of polyacenes. Therefore, even if the concentration of dopants is low, it is likely to exhibit a sufficient conductive property.
Condensed polycyclic aromatic compounds such as polyacenes, however, have a very poor solubility and are hardly soluble, when no substituent is introduced therein. For this reason, there is a limit to synthesis methods using such condensed polycyclic aromatic compounds, and it was extremely difficult to process these compounds. It has thus been desired to introduce substituents on the side chains of condensed polycyclic aromatic compounds to improve the solubility strikingly, and to produce polyacenes suitable for easy synthesis and processing. In particular, any process for synthesis of sequentially increasing the number of condensed benzene rings while introducing substituents therein was unknown.
Heretofore, a means for introducing optional substituents at optional positions of polyacenes such as anthracene, naphthacene, pentacene, etc. has been limited to the Diels-Alder reaction.
For example, a process of producing decamethylanthracene is described in Harold Hart, et al., “Decamethylanthracene and its 10-‘Dewar’ Isomer,” Tetrahedron Letter, No. 36, pp. 3143-3146. According to this process, the Diels-Alder reaction was applied to introduce methyl group into anthracene. Likewise in Tetrahedron, Vol. 43, No. 22, pp. 5403-5214, methyl group or the like was introduced into polyacenes by using the Diels-Alder reaction.
In the Diels-Alder reaction, there was a limit to substituents that can be introduced onto side chains. With respect to carbon atoms that can be substituted onto side chains, their latitude was limited as well. Further in the Diels-Alder reaction, it is impossible to increase the number of condensed benzene rings sequentially. In the Diels-Alder reaction, it is necessary to design a scheme of synthesis, respectively, considering the individual structures of target compounds.
JPA Nos. H4-335087, H6-167807, H6-330032 and H10-36832 disclose substituted naphthacenes, and JPA No. H11-354277 discloses substituted pentacenes. However, these compounds were all synthesized based on classic methods of synthesis, and substituents that could be introduced or positions at which substituents could be introduced were limited. And any process of synthesis for sequentially increasing the number of condensed benzene rings while introducing substituents was not disclosed, either.